Ink jet printing is a conventional technique by which printing is normally accomplished without contact between the printing apparatus and the medium on which the desired print characters are deposited. Such printing is accomplished by ejecting ink from an ink jet printhead of the printing apparatus via numerous methods which employ, for example, pressurized nozzles, electrostatic fields, piezo-electric elements and/or heaters for vapor phase bubble formation.
The ink compositions used in ink jet printing typically employ water, colorants and low molecular weight water-miscible solvents. The colorants which may be employed include dyes or pigments. It is desirable for consumers to have the ability to print faster. The ability to print faster, however, often requires ink compositions that dry and/or penetrate the print media fast. Such fast drying ink compositions unfortunately tend to result in poor print quality. Additionally, faster drying/penetrating inks often interfere with parts of the printing apparatus, causing, for example, poor print images.
It is of increasing interest to develop ink compositions that are not carcinogenic, dry fast, do not interfere with the printing apparatus and result in excellent print quality. This invention, therefore, is directed to novel ink compositions and particularly aqueous ink compositions which unexpectedly dry fast and/or result in excellent print quality without interfering with parts of printing apparatuses. Moreover, the instant invention is directed to a novel colorant set that results in inks capable of being printed from, for example, an ink jet printer, whereby the colorants which make up the colorant set are not, as often found, benzidine based. Further, it has been unexpectedly discovered that the superior results of the inks described in this invention are not dependent upon the addition of a surface active agent, particularly a polyoxyethylene polypropylene block co-polymer, which is not required to disperse a pigment.